Tapping machine



H. J. WOOCK TAPPING MACHINE May 5, 1953 2 SHEETSSHEET 1 Filed April 4. 1949 INVEN TOR. $5528 27 J W 061:,

TOQNEY- H. J. WOOCK TAPPING MACHINE May 5, 1953 2 SHEETS-SHEET 2 Filed April 4. 1949 INVENTOR. 2771 [46008.

5 BY '2 l .r

A TORNEY- Patented May 5, 1953 UNITED STATES FATENT OFFICE TAPPING MACHINE Herbert J. Woock, Arcadia, Calif.

Application April 4, 1949, Serial No. 85,431

13 Claims. 1

The present invention relates to tapping machines in general and includes attachments by which drill presses, screw machines, lathes and the like can be converted into tapping machines. More specifically the invention comprises a tapping machine incorporating a plurality of leadscrews which may be selectively connected in operative relationship to the rotary spindle at any position within its range of longitudinal displacement to enable the machine to cut threads of different pitch at any spindle projection.

Holes may be tapped by the operation of handor power-driven tapping machines. Any powerdriven drill press or rotary machine can function to tap holes by the use of a proper holding fixture by which the tap is secured to the machine spindle. Where holes are tapped by such machines, and the tap functions to draw itself into the hole at the same time it cuts the thread,

it is found that the thread is not perfect. This is particularly true in tapping holes in certain metals and while the resulting thread may be acceptable for ordinary work it is not sufficiently accurate for precision work.

To provide the requisite thread accuracy for precision work special tapping machines have been designed, and also special attachments have been provided for drill presses and the like, which employ a leadscrew to advance the spindle and the tap carried thereby into the work. The

leadscrew has a pitch duplicating the pitch of the thread of the tap being used so that the tap functions only to cut the thread and does not draw itself into the hole, the advance being provided by the leadscrew. Threads so made can be perfect but heretofore certain difficulties have been present in the machines and in such attachments.

The majority of the special tapping machines of the type referred to are designed especially for reaming and tapping only. This means that the hole to be threaded must be drilled by some other machine and then removed to the tapper for the reaming and tapping operation. Accordingly at least two machines are required thereby materially increasing the opportunity for errors and misalignments which result in inaccurate threads. Clearly a hole threaded by a tap not perfectly aligned will not be a perfectly tapped hole. It is equally clear if the part to be tapped is removed from a first holding fixture in which it was drilled and then placed in a second fixture in another machine for purposes of tapping the opportunity for misalignment is increased.

Frequently it is necessary to tap several holes in one part which holes may be of different sizes and which may require threads of different pitch. In the conventional machine it is necessary to change the leadscrew at the expenditure of an appreciable time. Alternative y, if more than one piece is to be tapped all the holes of one size may be tapped in the various pieces with one leadscrew in place, the leadscrew changed, and the pieces again passed through the machine and the next hole tapped. In the one case an undesirable expenditure of time is required for each change of leadscrew while in the other case the possibility of error is greatly increased.

Where conventional tapping attachments are r used on drilling machines it is possible in many instances to drill, ream, and tap in one fitting to provide increased accuracy. But here also where more than one size of hole or pitch of thread is encountered it is necessary to remove the attachment, make a change of leadscrew therein, and then replace it.

An additional problem is encountered in the special tapping machines or in the special tapping attachments now available where the holes to be drilled and tapped are not on the same level. The leadscrew has a limited range of move ment and with the adjustment of the rotary spindle to accommodate Work at various levels the range of the leadscrew may be and frequently is exceeded. A single replaceable leadscrew is attached directly to the spindle in all accepted special tapping machines and in all accepted special tapping attachments now on the market. Accordingly, and while tapping with such machines and attachments, it is necessary to restrict spindle displacement to the range of the leadscrew which correspondingly restricts the range of travel toward and into the work.

With an appreciation of the problems present in tapping machines and in attachments by which other machines are converted for tapping purposes, and also with an appreciation of the defects characterizing such apparatuses heretofore upon the market, it is an object of the present invention to provide a new and improved tapping machine characterized by its ability to tap in all longitudinal positions of the rotary spindle.

It is another object of the invention to provide a new and improved tapping attachment for drill presses and the like capable of selectively controlling the advance of the tap-carrying spindle into the work.

Still another object of the invention is to provide a tapping machine in which the tap-carrying spindle is selectively advanced into the work at a rate determined selectively by the operator.

A further object of the invention is to provide a tapping machine in which the tap-carrying spindle is selectively connectible to various leadscrews of various pitches in all of its longitudinal positions.

Another object of the invention is to provide a tapping machine in which a longitudinally displaceable tap-connected spindle is selectively connectible to leadscrews of various pitches throughout its entire range of axial displacement.

A still further object of the invention is to provide a tapping machine in which the driven spindle is selectively connectible in all of its longitudinal positions to a plurality of leadscrews spaced along its length.

Still another object of the invention is to provide an attachment for machine tools, such as drill presses incorporating a rotatable spindle, including a plurality of leadscrews arranged to engage the spindle or an extension thereof and to be selectively connected thereto.

A further obect of the invention is to provide a tapping attachment for the convers on of drill presses and the like into tapping machines capable of cutting threads of various pitches.

A still further object of the invention is to provide a tapping attachment for machines, such as drill presses and the like, by which such machnes are rendered capable of advancing their spindles into the work at a rate corresponding to the pitch of the tap being used. the attachment being characterized by its ability to incorporate additional leadscrews as desired by the operator.

lhese and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawings to which they relate.

Referring now to the drawings in which preferred embodiments of the invention are illustrated:

Figure 1 is a vertical section through a tapping attachment constructed in accordance with the present in ention mounted upon a machine such as a drill press;

Figure 2 is a perspective view of one of the clutch dogs by which the leadscrews are connected to the rotary spindle;

Figure 3 is a transverse se-tion through the spindle upon the line 33 of Figure 1;

Figure 4 is a schematic diagram of the control circuit by wh ch the leadscre s are selectively connected to the rotating spindle by hydraulically actuated means;

Figure 5 is a schematic diagram of a modified control circuit in which the hydraulic actuating means of the circuit of Figure 4 are replaced by electrical means; and Figure 6 is a schematic diagram of the circuit for the drivin motor by which its direction of rotation is controlled.

In the drawin s a po er-driven machine is indicated generally by the reference character In and the driven rotary spindle, or a connected extension thereof, indicated by the reference character I2, extends upwardly through its top plate ll. Machine I 0 may be a drill press or similar machine of the type incorporating a rotary shaft or sp ndle, and while in the illustrated form is shown with a vertical shaft it is to be understood that its axis can as well be horizontal or inclined. The spindle I2 may be of the machine shaft or an extension fixedly connected thereto and in effect integral therewith. For reasons which will be made clear the spindle is provided upon its surface with adjacent circumferential grooves 13, the sides of which in a preferred form taper at angles of thirty degrees to a normal plane. It is also provided with circumferentially spaced longitudinal grooves or channels [4, as illustrated in Figure 3, which may also be referred to as flutes. The longitudinal and circular grooves intersect and as both are relatively small and closely spaced the exterior surface of the spindle appears as small pyramids arranged in straight rows both longitudinally and circumferentially.

At the unshown lower end of spindle l2 would normally be positioned a. conventional quick change chuck adapted to hold drills, reamers, and taps as desired. The tapping attachment is positioned upon the top of machine It resting upon the top plate II. It in fact comprises a plurality of similar stacked units, two in the illustrated embodiment, although it is to be understood that the number can be increased as desired. The units are indicated generally by the reference character 15 and each includes a principal frame, casing or housing member [6 encircling spindle |2 in spaced relationship preferably, but not necessarily, circular. Casing members it are provided top and bottom with outwardly extending brackets or flanges ll. Each unit l5 also includes a top member or plate l8 fixed to the upper flange of each casing l6 and centrally bored and threaded at [9 to function in each instance as a fixed nut for a cooperating leadscrew to be described. Accordingly, the plate may be referred to as the leadscrew nut.

Where the top and bottom of two units I 5 abut, the top plate H! of the lower unit also functions as the bottom plate for the upper unit, the two units being held in assembled relationship by threaded bolts 2| which extend between apposed flanges I l and through the intermediate plate IS. The lower unit I5 is secured to a bottom or attachment plate 23 by means of bolts 24, the plate in turn being secured by bolts 26 to the top plate ll of machine It]. Upper unit [5 carries a cover 21 the peripheral flan e of which is secured by bolts 39 to the adjacent top plate It and with the latter to the adjacent casing IS. The cover is provided with a central cylindrical sleeve portion seating the outer part 28 of a bearing having a circumferential flange mounted on the end of the cover sleeve by bolts 29. Bearing part 28 can be and preferably is fo med of two halves.

The cooperating inner part of the bearing is indicated by the reference character 3! and is provided with end flanges 32 abutting the ends of outer bearing part 28 to prevent its own axial displacement. Bearing part 3| rotates with spindle [2 being keyed thereto by a key 33 seated within an extension of one of the longitudinal flutes M. Key 33 being slidable in the flute provides a relationship in which the bearing inner part 3| rotates with the shaft while permitting the shaft to be displaced longitudinally.

Within each casing l6 of each unit I5 is slidably mounted a cam 36. The inner surface of the cam must be circular and is seen to have a large diameter upper end and a small diameter lower end, the surfaces of different diameter being connected by a sloping surface. The outer surface of cam 36 seats slidably in the frame I 6 and conforms to the supporting surface thereof. If the supporting surface of frame I6 is circular then so long as the cam is slidable in the frame in adirection parallel to the longitudinal axis of spindle [2. In its uppermost position cam abuts the overlying top plate I8 and in its lower position the unit bottom plate, formed in an upper or intermediate unit by the top plate [-8- of the unit below, and in the lowermost unit by a bottom plate 23.

A plurality of laterally extending trunnions 31 are fixed in each of the cams 35 and extend out.- wardly through slots 38 in the enclosing frame or casing l6. Theouter end of each trunnion is fixed to a piston 41 of a pressure-actuated l 1y. draulic ram which includes a cylinder 42 mounted fixedly upon the bottom flange ll of the adjacent casing I5. Each cylinder is connected by a; conduit 43 to a source of fluid under pressure, either liquid or gas, and each piston M includes a sealing gasket at its inner end which provides a fluid-tight fit within the cylinder. The piston M is normally retained, in the absence of fluid under pressure within the cylinder 42, at its innermost position under the force exerted by an abutting concentric coil spring 45 seated between it and the overlying frame flange ll. This innermost and normal, position is illustrated in the lower unit [5 of Figure 1 and it is to be noted that with the piston so positioned the trunnion 3'! has moved the cam 36 downwardly to its lowermost position. In the upper unit l5 of Figure 1 the pistons 4'! are illustrated in their upper or outer positions in which they are retained by fluid under pressure within cylinder 42 and against the action of springs 46 which are compressed. In this position the pistons 41 have moved the connected cam 35 to its uppermost position.

Each unit [5 includes a leadscrew 5| formed as an externally threaded sleeve rotatably seated within the threaded bore IQ of the unit leadscrew nut l8. Leadscrews 51 extend concentric to and in spaced relationship with spindle l2 being provided at their lower ends with laterally extending centrally bored bosses form ng seats 52 for radially extending clutch dogs 53 slidably positioned therein. Each dog 53 is provided at its inner end with transversely extending V- shaped ribs 54 adapted to mesh with longitudinal and circumferential spindle grooves l3 and It. At its outer end each dog has a fixed enlarged head 55 which encloses and rotatably seats a ball bearing 51. A concentric coil spring 58 is positioned between each head 56 and a circumferential flange 59 upon a dog seat 52 and at all times exerts a force to urge the dog radially outwardly from the spindle l2 and the bearing 57 against cam 36. With cam 36 in its lower position, as illustrated in the lower unit I5 of Figure 1, the balls 51 abut the cam surface of larger diameter and the inner end of the dog is disengaged from the spindle. In upper unit l5 the balls are shown in contact with the lower small diameter surface of the cam and have been moved radially in:- wardly, the springs 58 being; compressed, and the ribs 5-4 engage the spindle. In the latter relation ship the leadscrew 5| is connected by the dogs to the spindle t2; and rotates therewith, advancing upwardly or downwardly within its nut l8, depending upon the, direction of spindle rotation.

To reverse the direction of spindle rotation. after the leadscrew 5| has advanced its full travel. downwardly there is provided a limit switch, gen-. erally indicated by the reference character GI,

which may be of conventional design and includes rack-and-pinion positioning means 62 by which it can be positioned relatively to its carrying plate l8 under the control of a rotatable rod 63 extended transversely to the exterior of the attachment where it carries a knurled head 64. Switch BI is so positioned as to be contacted and closed by the circumferential flange 59 of the dog seat 52 as the leadscrew moves downwardly to its lowermost position whereupon the driving motor is reversed. The electrical circuit for this control is shown in Figure 6 in which the driving motor for the spindle l2 bears the character M and is seen to be connected to a reversing switch 66 the position of which is controlled by a solenoid 51 the winding of which is in series with a plurality of limiting switches Bl which are connected in parallel. With motor M energized and rotating in one direction, as for example to advance leadscrew 5| downwardly, the spindle continues its rotation until switch 6! is closed as described whereupon solenoid 61 is energized, reverses switch 66, and instantly motor M will reverse its direction of travel. Spindle I2 then returns the leadscrew to its initial position. The cycle of leadscrew travel is from the position illustrated in the lower unit l5 of Figure l to the position shown in the upper unit of the same figure and then back to the first position. R-eversing switch 66 is provided with a manually operable push button 69 by which the operator can manually reverse the direction of motor travel independently of the operation of limit switch Si.

Upon the return of the leadscrew to its starting position it must be declutched from the spindle and the dogs 53 moved to their outer positions. This is accomplished by releasing the fluid pressure within the ram cylinders t2 under control of a limit switch, indicated generally by the reference character ll, positioned immediately below the unit top plate H8 in position to be contacted and closed by the contact of a circular ring 12 fixedly carried by the dog seats 52. As the ring i2 is continuous it can contact and open the switch in any arcuate position of the leadscrew.

In Figure 4 the control circuit for the pressureactuated ram units is, illustrated and the flow of fluid under pressure through the conduits 43 to the cylinders 32 in each unit if: is seen to be under the control of a valve unit generally indicated by the reference character '55. Each unit l5; comprises a cylindrical casing Eli sup plied with fluid, either liquid or gas, under pressure through a conduit H from any suitable source or pressure-creating, means. Each of the conduits 43 from the ram units of a particular unit l5 connects to the cylinder 16 within which moves a piston valve 18 formed with a circumferential port '59 adapted to connect the conduit to either the. incoming pressure conduit ll or to the exhaust port as leading to atmosphere. A coil spring 83 at all times urges each piston 18 to an end position in which it connects the conduit 53 to the port ill to release the pressure within the ram unit. A connecting rod 86 on each piston also functions as the armature of a solenoid in which the winding as is so wound that when energized the piston it is displaced to the left, as viewed in Figure 4, to effect the closing of port 8i and the connection of conduit 43 to the pressure-carrying conduit Tl. With the valve so positioned the connected ram units are pressurized and their pistons 4! move from the position shown in the lower unit of Figure 1 to the position illustrated in the upper unit of the same figure.

The current-conducting leads 8! and 88 to each solenoid winding 86 connect respectively to a manually operable switch unit, indicated generally by the referenc character Eli, and to a selector switch indicated generally by the reference character 92. Those switches are in turn connected through leads 93 and 94, respectively, to a suitable source of electrical potential.

Selector switch 92 includes a manually adjustable contact adapted to close upon one of a plurality of stationary contacts each of which is connected to its own lead 88 leading to solenoid windings 83 of valves 15 controlling the pressureactuated ram units of different units 15. Depending upon the kind of thread to be tapped the operator positions the selector switch movable contact as to connect electrically the solonoid of the valve 15 operatively associated with that unit l having a leadscrew corresponding to that thread. In Figure 4 two units E5 are shown as connected by leads 88 to the selector switch. Additionally a plurality of leads 8d are illustrated which would be connected to addi-' tional units IS in a machine having a wider range of use.

Manually operable switch 9! controls the actual clutching of the leadscrew to the spindle after the operator has selected the unit iito be actuated. Switch 9| may be a conventional normally open switch including a blade 93" normally spring-held in open position and adapted to be closed by a push button 95. H is connected in parallel with switch 9! and is closed instantly by the leadscrew dis olacement effected by the closing of the latter. The operator may then release push button 95 so that switch 91 returns to open position, the how of current continuing to pass through switch ii.

In the operation of the described embodiment of the invention let it be assumed that the tapping attachment is positioned upon a drill press or similar machine Ill as illustrated in Figure 1. Let it also be assumed that the work is securely positioned at the lower end of spindle i2, or its extension, has been drilled and reamed, and that it is desired to tap the hole with a thread corresponding to the pitch of leadscrew iii of upper unit l5. As illustrated in Figure 1 the upper unit has already controlled a tapping operation and is just about to operate limit switch 6i so that the driving motor M will be reversed and the leadscrew fed back to its initial position. Let it be assumed, however, that the hole is untapped and that the leadscrews of both units 15 are in their upper positions illustrated in the lower unit [5.

The operator positions the control lever of selector switch 92 as illustrated in Figure 4 so that current will be conducted to the solenoid winding 85 controlling that valve '15 operatively associated with the ram units forming a part of the upper leadscrew unit [5. All of the upper limit switches ll are held in open position by the contact of the various leadscrew-carried rings 12. The machine being in operation and spindle l2 rotating the operator pushes button 95 whereupon normally open switch 91 is closed and winding 86 of the valve solenoid energized. Valve piston 18 is moved from its normal inoperative position, shown in the right-hand unit of Figure 4, to the position shown in the lefthand unit so that fluid under pressure from Limit switch conduit TI is directed through port 19 and connects conduit 43 to the ram cylinders 42. Ram pistons ll of upper unit I5 are thereupon forced upwardly from their normal inner position, in which they are held by springs 46 illustrated in the lower unit l5 of Figure 1, to their upper position. As the cam 36 is connected to the pistons by trunnions 31 it moves upwardly therewith. The balls 51 ride from the upper cam portion of maximum internal diameter onto the lower portion of lesser diameter and the dogs 53 are forced inwardly. The inner end of each dog, and specifically its ribs 54, engages the circular and longitudinal grooves in spindle l2 whereupon they, their carrying seats 52, and the leadscrew 5| integral therewith, rotate as a unit with the spindle.

At the time of the closing of the clutch of upper unit l5 its leadscrew 5| was in its uppermost position. With the spindle l2 rotating in the proper direction to perform the tapping operation the leadscrew advances downwardly, that is, toward the machine I0. As the leadscrew is locked by the dogs 53 to the spindle l2 the latter also advances downwardly forcing the tap at its lower end into the hole being tapped. The vertical displacement of spindle l2 in its upper bearing is permitted by the sliding movement of the key 33 in an extended flute in which it is positioned. Limit switch H closes instantly as the contact ring 72 moves therefrom efiiecting the closing of the circuit in parallel with the manually operable switch 9! which could then be opened by the operator releasing button 95.

As the leadscrew reaches its lower position, a variable determinable by the operator through the rotation of knurled knob 64, the limit switch 6! is closed. As is illustrated in Figure 6 this immediately causes current to flow through the winding of the solenoid 6! controlling reversing switch 66 which thereupon is reversed to effect the reversal of the direction of rotation of driving motor M. Spindle I2 then rotates in the opposite direction.

As spindle l 2 and leadscrew 5! remain clutched together for con oint movement the latter also reverses its direction of travel and moves from its lower position illustrated in the upper unit l5 of Figure 1 to its uppermost position as illustrated in the lower unit. As it moves into this uppermost position limit switch H is again opened by the contact of ring 12 whereupon the flow of current through winding 86 of the solenoid controlling valve 15 is cut off. Immediately spring 83 acting upon the valve piston 78 forces the latter from its operative position, as illustrated in the left-hand unit of Figure 4, to its inoperative position illustrated in the right-hand unit. In the latter position, it is noted, conduit 43 connects the ram units directly to atmospheric port 8| through the piston port 19. The pressure within the previously energized ram units is thereupon released and, under the actuation of coil springs 46, each piston 4! of the previously actuated ram units of upper unit I 5 travels from its position as illustrated in Figure 1 to the position illustrated in the lower unit l5. In its travel the piston 4|, more accurately the pistons 4!, again carries the cam 36 which, as it travels downwardly, permits the dogs 53 to move outwardly as the balls 51 roll from its surface of minimum internal radius to that of maximum radius. Under the actuation of coil spring 58 dogs 53 move outwardly and disengage ace-7,0512

i9 themselves from the spindle which thereupon rotates freely.

The entire machine is now returned to its initial relationship with the exception that spindle i2 is rotating in the reverse direction. The operator can again reverse the direction of rotation by depressing push button :69 :connected to reversing switch =56 which effects the return of that element to its .originalrelationship and again reverses the direction of travel of motor M so that the described operation can be re.- peated upon the next hole to .betapped.

Referring now to Figurefi in;parti.cular a;modified controlcircuit is illustrated which may :be considered as identical to that illustrated in Figure 4 with the exception that the hydraulic features have been eliminated and :the valve:- actuating solenoid winding "36 replaced by a winding Hi! acting directly upon the piston M. In the first embodiment the energizationgof winding 86 positioned valve unit 1:5 so thate:the fluild under pressure actuatedrthe ram piston. In this embodiment the energization-of -.a pairoi .windings Ml acts upon the-pistonsii connectedyto the cam 3E and positions it.directly -rather1than byacting through the intermediary of the; fluidpressure-actuated means. In other respects the characteristic and operation of this modified form are identical to that first described.

The provision of the operator-adjustable c oni trol for the circuit'switch 64 of each leadscrew unit 15 enables the operator to vary the travel of the tap carried by. spindle 12 or its extension. The. presence of -a plurality .of units [5. iaspreviously described,v makes unnecessary the disassembly of the machine, in fact makes unnecessary any mechanical change in the machine; to render it operable to-tap threads of different pitch. The stacked construction makes itpossible to extend the field of usefulness of the machine zbyuaddin'g additional leadscrew :units I15 to-those already present in the machine. .iElach unit isrindependently operableand'can.bezclutchedq to the spindle atany place along the :length ofathelatterithereby greatly increasing the-flexibilityvof,the..machine in use throughenablingit toitap holes :at difieringheights. I'I-n the illustrated embodiment of the inventionis 1 an attachment mounted :on a drill press or similar .tool, but: therprinciples involved are applicable to oonstructionsrincorporrated in'a tapping machine as a permanent part.

While the particular apparatus herein shown and described in detail is =fu11y -capableof attaining the objects and providing:the advantages hereinbefore stated, it is to be understood that it is merelyillustrative of the presently preferred embodiments of the invention and. that no'llir'nitations are intended'to thedet'ails of construction or design herein shown other-than as definedin the appended claims.

I claim:

1. Ina tapping machinelof the type including a body and a driven rotary taprconnected spindle carried thereby for rotation .arid for axialidisplacement, a plurality of leadscrew units tomove said spindle axially spaced therealong and each including a rotatable leadscrew having threads of a different pitch than that of the leadscrews of the other units and also including a fixed leadscrew nut seating said leadscrew, clutch means carried by each of said leadscrews including a movable element engageable in one position with said spindle to effect its conjoint rotation and longitudinal displacement with the connected leadscrew, cylindrical cam means concentric to said spindle and having cam surfaces of different diameters to abut said element and determine its position relative to said spindle, said element traveling circularly in abutting contact with said cam when in engagement with said spindle, and operator-controlled means to effect the displace;- ment of said cam means longitudinally of said spindle to movesaid element relative thereto.

2. The construction recited in claim '1 characterized .in that means are provided to reverse the direction of rotation of said spindle after conjoint rotation with said connected leadscrew effecting a predetermined displacement of said leadscrew relativeto-said nut and an equivalent longitudinal displacement of said spindle.

ii/The constructien recited in claim ,2 characteizcd in that means are provided to effect the isplacement of said cam to disengage said element from said spindle upon thereturnofsaid connected leadscrew ,toits initial position following the reversal in dircctionoi rotation of said p n l el. An attachment for the conversion .oia drill press or the like having a rotary axially displaceblespindle into a tappin machine, comprising a plurality of separable leadscrew units secured ingstaclrecl relationship and adaptedto enclose an extendedend of said spindle, each of said units including its own l'lOYl-rl'GtfltfiblG leadscrew .nut and a leadscrewthreadedly seated therein, .and movable relative theretoaxially of said spindle upon being rotated, the leadscrews otdiflerent units having. threads of different pitch; that their rates of-axialrdisplacemcnt will diifenforoa .g-iuen speed of rotation, and.operatorecontrolledVindirectly actuated means selectively to connect. said leadscrews: to .said spindle during itsrotation.

.5. The construction. recited inclaimd characterized in that -each of said units include .av limit switch positioned as to becontaoted and operated upon a predetermined displacement .oisaid leadscrewandiadapted to-be included inan electrical circuit controllingthe 'clirection-of rotation. of saidspindle.

6. The. construction-recited .in claim 4 characterized in that each of said units includes a limit switch positioned as to be-contacted and operated upon'the return of said leadscrew to-its-ini-tial position and adapted to be included in an electrical circuit-controlling the connection .of-said leadso-rewto said spindle.

in atapping machine of the type including a body portion and-a driven-rotary spindle'carried' thereby for rotation and axialdisplacement relative to the-body portion, -moter means for efiecting' continuous rotation of the spindle, and means for selectively effectingaxial-displacement of the, spindle at'different rates during rotation ofthe spindle comprising a plurality of leadscrew units continuously carriedby saidbody for alternative cooperation with said spindle, each including a stationary threaded part and a rotatable threaded part inengageinent therewith, clutch means toengage said units indiidual t saidsrind p urins it I r at on a i operator-controlled means to actuate said clutch means to connect said units selectively to said spindle, characterized in that each of said units includes a clutch element rotatable with said rotatable threaded part and movable between spindle-engaging and non-engagin positions, and in that each of said units also includes an independently actuated cam to control the position of said clutch element.

3. In a tapping machine of the type including a body portion and a driven rotary tap-connected spindle carried thereby for rotation and for axial displacement relative to the body portion, motor means for effecting continuous rotation of the spindle, and means for selectively effecting axial displacement of the spindle at different rates during rotation of the spindle comprising a plurality of leadscrew units spaced therealong and each including a rotatable leadscrew having threads of a difierent pitch than that of the leadscrews of the other units and also including a fixed leadscrew nut seating said leadscrew, clutch means carried by each of said leadscrews including a transversely extending element rotatable with said spindle movable between spindle-engaging and non-engaging positions, a nonrotating cam abutting said element and movable to position it in spindle-engaging position, and control means to position said cam.

9. In a tapping machine of the type including a body portion and a driven rotary tap-connected spindle carried thereby for rotation and for axial displacement relative to the body portion, motor means for effecting continuous rotation of the spindle, and means for selectively eifecting axial displacement of the spindle at diiierent rates during rotation of the spindle comprising a plurality of leadscrew units spaced therealong and each including a rotatable leadscrew having threads of a different pitch than that of the leadscrews of the other units and also including a fixed leadscrew nut threadedly seating said leadscrew, clutch means carried by each of said leadscrews including a movable element engageable in one position with said spindle to effect its conjoint rotation and longitudinal displacement with the connected leadscrew, a cam concentric with said spindle and displaceable longitudinally of said spindle to position said element relative to said spindle, and operator-controlled means to position said cam.

10. An attachment for the conversion of a drill press or the like having a rotary axially displaceable spindle into a tapping machine, and motor means for continuously rotating the spindle to efiect the drilling operation, said attachment comprising means for selectively effecting axial displacement of the spindle at difierent rates to perform various tapping operations using the same spindle, and including a plurality of individual and separable leadscrew units secured in stacked relationship and adapted to enclose an extended end of said spindle, each of said units including a non-rotatable leadscrew nut and a leadscrew threadedly seated therein, the leadscrews of difierent units having threads of difierent pitch so that their rates of axial displacement will differ for a given speed of rotation, clutch means operable during rotation of the spindle and carried by each of said leadscrews to connect it to said spindle to move it axially upon the rotation of said leadscrew, each of said units including its own remote controlled clutch-actuating means including fluid-pressure-operated means.

11. An attachment for the conversion of a drill press or the like having a rotary axially displaceable spindle into a tapping machine, and motor means for continuously rotating the spindle to effect the drilling operation, said attachment comprising means for selectively efiecting axial displacement of the spindle at different rates to perform various tapping operations using the same spindle, and including a plurality of individual and separable leadscrew units secured in stacked relationship and adapted to enclose an extended end of said spindle, each of said units including a non-rotatable leadscrew nut and a leadscrew threadedly seated therein, the leadscrews of difierent units having threads of difierent pitch so that their rates of axial displacement will differ for a given speed of rotation, cooperating clutch means including a radially displaceable element carried by each of said leadscrews to connect it to said spindle, each of said units including its own clutch-actuating means to displace said element radially during spindle rotation and inoludin electrically actuated means.

12. In a machine for tapping, a body, a rotary longitudinally displaceable tap-connected spindle, a reversible driving motor for said spindle, and means for selectively effecting axial displacement of the spindle at different rates during rotation of the spindle comprising a plurality of non-rotatable fixed leadscrew nuts spaced longitudinally along said spindle concentrically thereof, a sleeve leadscrew concentric to said spindle seated threadedly in each of said nuts, the threads of said leadscrews having different pitches to effect different rates of longitudinal displacement for a given rate of rotation, each of said leadscrews carrying a radially displaceable dog engageable with said spindle in its inner position to clutch the connected leadscrew to said spindle for conjoint rotation and longitudinal displacement at a plurality of specific points, a cylindrical cam encircling each of said leadscrews mounted for longitudinal displacement independently thereof and determining the radial position of said dog, and individual means to position said cams under the control of the operator.

13. The construction recited in claim 12, characterized in that the spindle has a plurality of longitudinally and transversely extending grooves, and said dogs each have cooperable groove-engaging teeth.

HERBERT J. WOOCK.

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